Imprints of pandemic lockdown on subsurface water quality in the coastal industrial city of Tuticorin, south India: A revival perspective

Abstract

Globally, incidences of environmental improvements owing to seizing the anthropogenic activities during the lockdown have been reported through news articles, and photographs, yet a formal scholarly study has been lacking to substantiate the imprints of lockdown. We hereby present the imprints of lockdown period on water quality (both chemical and biological) parameters during the nationwide lockdown (COVID -19 epidemic) in India between 25th March to 30th May 2020. The present study describes the changes in chemical and biological water quality parameters based on twenty -two groundwater samples of a costal industrial city of Tuticorin in Southern India, taken before (10 -11th February, 2020) and during the lockdown (19 -20th April 2020) periods. Parameters compared are pH, total dissolved solids (TDS) and electrical conductivity (EC), nitrate (NO 3), fluoride (F), chromium (Cr), iron (Fe), copper (Cu), zinc (Zn), cadmium (Cd), lead (Pb), arsenic (As), and selenium (Se); and bacterial parameters like total coliforms, fecal coliforms, E. coli, and fecal streptococci . Among the metals, the significant reductions in Se (42%), As (51%), Fe (60%) and Pb (50%) were noticed probably owing to no or very less wastewater discharges from metal -based industries, seafood -based industries and thermal power plants during the lockdown. Reduction in NO 3 (56%), total coliform (52%) and fecal coliforms (48%) indicated less organic sewage from the fishing industries. Contents of Cr, Cu, Zn and Cd, however, remained similar and fluoride did not show any change, probably as they were sourced from rock -water interactions. Similarly, we did not observe alterations in E. coli and fecal streptococci due to no significant change in domestic sewage production during the lockdown. Finally, the multivariate analyses aptly illustrate that while principal component analyses identify different four sources operating in the area, the difference among the different water qualities start diminishing during the lockdown. The study implies that groundwater is definitely under active interaction with surface waters and thus a quick revival could be observed following the seizing of anthropogenic activities during lockdown.